Fin cut for taper device

ABSTRACT

A method of making a semiconductor device includes patterning a fin in a substrate; performing a first etch to remove a portion of the fin to cut the fin into a first cut fin and a second cut fin, the first cut fin having a first and second fin end and the second cut fin having a first and second fin ends; forming an oxide layer along an endwall of the first fin end and an endwall of the second fin end of the first cut fin, and an endwall of the first fin end and an endwall of the second fin end of the second cut fin; disposing a liner onto the oxide layer disposed onto the endwall of the first fin end of the first cut fin to form a bilayer liner; and performing a second etch to remove a portion of the second cut fin.

PRIORITY

This application is a continuation of and claims priority from U.S.patent application Ser. No. 15/073,065, filed on Mar. 17, 2016, entitled“FIN CUT FOR TAPER DEVICE,” which is a continuation of and claimspriority from U.S. patent application Ser. No. 14/841,951, filed on Sep.1, 2015, entitled “FIN CUT FOR TAPER DEVICE”, each application isincorporated herein by reference.

BACKGROUND

The present invention relates to metal-oxide-semiconductor field-effecttransistors (MOSFET), and more specifically, to fin-type field-effecttransistors (FinFET).

The MOSFET is a transistor used for amplifying or switching electronicsignals. The MOSFET has a source, a drain, and a metal oxide gateelectrode. The metal gate is electrically insulated from the mainsemiconductor n-channel or p-channel by a thin layer of insulatingmaterial, for example, silicon dioxide or glass, which makes the inputresistance of the MOSFET relatively high. The gate voltage controlswhether the path from drain to source is an open circuit (“off”) or aresistive path (“on”).

The FinFET is a type of MOSFET. The FinFET is a double-gatesilicon-on-insulator (SOI) device that mitigates the effects of shortchannels and reduces drain-induced barrier lowering. The “fin” refers tothe narrow channel between source and drain regions. A thin insulatingoxide layer on either side of the fin separates the fin from the gate.

SUMMARY

According to an embodiment, a method of making a semiconductor deviceincludes patterning a fin in a substrate; performing a first etchingprocess to remove a portion of the fin to cut the fin into a first cutfin and a second cut fin, the first cut fin having a first fin end and asecond fin end and the second cut fin having a first fin end and asecond fin end; forming an oxide layer along an endwall of the first finend and an endwall of the second fin end of the first cut fin, and anendwall of the first fin end and an endwall of the second fin end of thesecond cut fin; disposing a liner onto the oxide layer disposed onto theendwall of the first fin end of the first cut fin to form a bilayerliner; and performing a second etching process to remove a portion ofthe second cut fin.

According to another embodiment, a method of making a semiconductordevice includes patterning a fin in a substrate; removing a portion ofthe fin to define a first exposed end and a second exposed end;oxidizing a portion of the first exposed end and the second exposed endto form an oxide layer; disposing a liner over a portion of the oxidelayer; and performing a second etching process to remove a portion ofthe fin.

Yet, according to another embodiment, a semiconductor device includes afin patterned in a substrate, the fin having a first distal endpartially defining a first endwall and a second distal end partiallydefining a second endwall; a bilayer liner disposed onto the firstendwall of the first distal end; and a monolayer liner disposed onto thesecond endwall of the second distal end.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The forgoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIGS. 1A-1F illustrate an exemplary conventional method of cutting fins,in which:

FIG. 1A is a top view of fins arranged in a fin array;

FIG. 1B is a top view after patterning a mask over the fins;

FIGS. 1C and 1D are cross-sectional side views through the X-axis andY-axis, respectively, of FIG. 1B after performing an anisotropic fincut;

FIGS. 1E and 1F are cross-sectional side views through the X-axis andY-axis, respectively, of FIG. 1B after performing an isotropic fin cut;

FIGS. 2A-12D illustrate exemplary methods of making semiconductordevices according to embodiments of the present invention, in which:

FIG. 2A is a top view of fins with hard masks disposed over the fins;

FIGS. 2B and 2C are cross-sectional side views through the X-axis andY-axis, respectively, of FIG. 2A;

FIG. 3A is a top view of fin cut openings patterned in a mask disposedover the fins;

FIG. 3B is an expanded view of a fin cut opening of FIG. 3A with anideal mask overlay;

FIG. 3C is an expanded view of the fin cut opening of FIG. 3A with apoor mask overlay;

FIG. 4A is a top view after cutting the fins and removing the mask;

FIGS. 4B and 4C are cross-sectional side views through the X-axis andY-axis, respectively, of FIG. 4A;

FIG. 5A is a top view after oxidizing the end portions of the cut fins;

FIGS. 5B and 5C are cross-sectional side views through the X-axis andY-axis, respectively, of FIG. 5A;

FIG. 6A is a top view after disposing a liner and a planarization layerover the fins;

FIGS. 6B, 6C, and 6D are cross-sectional side views through the X-axis,Y-axis, and Z-axis, respectively, of FIG. 6A;

FIG. 7A is a top view after patterning and etching the planarizationlayer;

FIGS. 7B, 7C, and 7D are cross-sectional side views through the X-axis,Y-axis, and Z-axis, respectively, of FIG. 7A;

FIGS. 8A, 8B, and 8C are cross-sectional side views through the X-axis,Y-axis, and Z-axis, respectively, after removing the liner and hardmasks over the fins beneath the mask opening;

FIGS. 9A, 9B, and 9C are cross-sectional side views through the X-axis,Y-axis, and Z-axis, respectively, after removing the planarizationlayer;

FIGS. 10A, 10B, and 10C are cross-sectional side views through theX-axis, Y-axis, and Z-axis, respectively, after removing the finmaterial beneath the mask opening;

FIGS. 11A, 11B, and 11C are cross-sectional side views through theX-axis, Y-axis, and Z-axis, respectively, after filling the open finregions with an oxide;

FIG. 12A is a top view after recessing the oxide to reveal the uncutfins; and

FIGS. 12B, 12C, and 12D are cross-sectional side views through theX-axis, Y-axis, and Z-axis, respectively, of FIG. 12A.

DETAILED DESCRIPTION

Conventional methods for cutting fins for FinFET devices may havedrawbacks, including for example, mask overlay misalignment. FIGS. 1A-1Fillustrate an exemplary conventional method of cutting fins 101. FIG. 1Ais a top view of fins 101 arranged in a fin array. The fins 101 arepatterned in a substrate 102, as shown in FIGS. 1C-1F, and surrounded byshallow trench isolation (STI) regions 130. A fin cap 122 comprising ahard mask material is formed over the fins 101.

FIG. 1B is a top view after disposing a mask 105 over the fins 101. Themask 105 is patterned to form a mask pattern 103 (fin cut opening) andto expose a portion of the fins 101 beneath the mask 105. The maskpattern 103 represents an ideal mask overlay for cutting fins 101because the entire width 106 of each fin is exposed beneath the maskpattern 103. In practical application, however, cutting the fins 101using anisotropic and isotropic cutting methods presents challengesbecause the mask overlay may not be ideal. When the mask 105 ismisaligned, the entire width 106 of each fin will not be exposed, whichmay result in partial fin cutting.

FIGS. 1C and 1D are cross-sectional side views through the X-axis andY-axis, respectively, of FIG. 1B after performing an anisotropic fincut. An anisotropic etching process, for example, reactive ion etching(RIE), ion beam etching, or laser ablation, may be employed to performthe anisotropic fin cut. Although the fin cut region 141 in the Y-axisdirection (FIG. 1D) is clean and complete (substantially the entire fin101 is removed), the fin cut region 141 in the X-axis direction (FIG.1C) leaves residual fin material 142 or creates undesired fin damage dueto mask pattern 103 misalignment and the etching angle.

FIGS. 1E and 1F are cross-sectional side views through the X-axis andY-axis, respectively, of FIG. 1B after performing an isotropic fin cut.An isotropic etching process, for example, a chemical process employinga chemical etchant may be employed to make the isotropic fin cut.Although the material forming the fins 101 beneath the mask pattern 103is cleanly removed in the X-axis direction (FIG. 1E), unintended finundercuts in the region 142 may occur.

Accordingly, various embodiments provide methods of cutting fins (orremoving undesired fin portions) without jeopardizing the desired finportions in devices with closely spaced fins. Thermal oxidation is usedto seal fin ends in a two-step fin cutting method including anisotropicand isotropic etching processes. Thermal oxidation protects the fins toensure substantially complete removal of undesired fin portions. Likereference numerals refer to like elements across different embodiments.

The following definitions and abbreviations are to be used for theinterpretation of the claims and the specification. As used herein, theterms “comprises,” “comprising,” “includes,” “including,” “has,”“having,” “contains” or “containing,” or any other variation thereof,are intended to cover a non-exclusive inclusion. For example, acomposition, a mixture, process, method, article, or apparatus thatcomprises a list of elements is not necessarily limited to only thoseelements but can include other elements not expressly listed or inherentto such composition, mixture, process, method, article, or apparatus.

As used herein, the articles “a” and “an” preceding an element orcomponent are intended to be nonrestrictive regarding the number ofinstances (i.e. occurrences) of the element or component. Therefore, “a”or “an” should be read to include one or at least one, and the singularword form of the element or component also includes the plural unlessthe number is obviously meant to be singular.

As used herein, the terms “invention” or “present invention” arenon-limiting terms and not intended to refer to any single aspect of theparticular invention but encompass all possible aspects as described inthe specification and the claims.

As used herein, the term “about” modifying the quantity of aningredient, component, or reactant of the invention employed refers tovariation in the numerical quantity that can occur, for example, throughtypical measuring and liquid handling procedures used for makingconcentrates or solutions. Furthermore, variation can occur frominadvertent error in measuring procedures, differences in themanufacture, source, or purity of the ingredients employed to make thecompositions or carry out the methods, and the like. In one aspect, theterm “about” means within 10% of the reported numerical value. Inanother aspect, the term “about” means within 5% of the reportednumerical value. Yet, in another aspect, the term “about” means within10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% of the reported numerical value.

Turning again to the Figures, FIGS. 2A-12D illustrate exemplary methodsof making semiconductor devices according to various embodiments. FIG.2A is a top view of fins 201 with hard masks 222 disposed over the fins201. FIGS. 2B and 2C are cross-sectional side views through the X-axisand Y-axis, respectively, of FIG. 2A.

The fins 201 are patterned in a substrate 202. Non-limiting examples ofsuitable substrate 202 materials include silicon, sapphire, germanium,gallium arsenide, silicon germanium, indium arsenide, indium phosphide,or any combination thereof. The fins 201 may be formed in the substrate202 by depositing a hard mask 222 material over the substrate 202. Thehard mask 222 material forms a fin cap. Non-limiting examples ofsuitable materials for the hard mask 222 (fin caps) include silicondioxide, silicon nitride, or any combination thereof. In one embodiment,a mask is disposed over the hard mask 222 material and patterned and areactive ion etching (RIE) process is employed to form one or more fins201 in a fin array. The fins 201 may be arranged in substantiallyparallel rows as shown in FIG. 2A.

An oxide material is deposited around the fins 201 to form the STIregions 230. Non-limiting examples of suitable oxide materials for theSTI regions 230 include silicon dioxide, tetraethylorthosilicate (TEOS)oxide, high aspect ratio plasma (HARP) oxide, silicon oxide, hightemperature oxide (HTO), high density plasma (HDP) oxide, oxides formedby an atomic layer deposition (ALD) process, or any combination thereof.

FIG. 3A is a top view of fin cut openings 310, 311, 312 patterned in amask 301 disposed over the fins 201. The mask 301 may be, for example, aresist material (e.g., a photoresist material). The mask 301 ispatterned by etching to remove the mask 301 material in a desiredpattern. When the mask 301 is a photoresist, the mask 301 is patternedby exposing the mask 301 to a desired pattern of radiation. Then theexposed photoresist is developed with a resist developer to provide apatterned photoresist with fin cut openings 310, 311, 312. The fin cutopenings 310, 311, 312 expose the fins 201 beneath that will be cut. Thefin cut openings 310, 311 are used to cut the ends of the fins 201. Thefin cut opening 312 are used to cut a single fin 201 into two shorterlength fins. The fin cut openings 310, 311, 312 may be patterned in anydesired position over the fins 201 and are not limited to the ends ofthe fins 201 or to the middle of the fins 201. As long as three openingsare patterned to cut the fins 201 in three different locations along thelength of the fins 201. Cutting the fins 201 through fin cut opening 312will cut a single fin into two shorter fins. Cutting the fins 201through fin cut openings 310, 311 will shorten fins 201 and reveal endsof the fins 201.

FIG. 3B is an expanded view of FIG. 3A showing the region 320 around thefin cut opening 312 with an ideal or preferred mask 301 overlay. Thefins 201 beneath the hard masks 222 are exposed across the entire width330 to enable a clean fin cut.

FIG. 3C is an expanded view of FIG. 3A showing the region 320 around thefin cut opening 312 with a poor mask 301 overlay. One fin 201 beneaththe hard mask 222 is partially exposed across the partial width 331through fin cut opening 321. Another fin 201 is exposed across theentire width 330. The poor mask overlay will result in the fins 201 onlybeing partially cut.

FIG. 4A is a top view after cutting the fins 201 through the fin cutopenings 310, 311, 312 and removing the mask 301. FIG. 4A illustratescutting the fins 201 through the poor mask 301 overlay of FIG. 3C. FIGS.4B and 4C are cross-sectional side views through the X-axis and Y-axis,respectively, of FIG. 4A.

The fins 201 and hard mask 222 are removed in the region beneath the fincut openings 310, 311, 312 by employing a dry etching process, forexample, and anisotropic etching process (first etching process). Theanisotropic etching process may be, for example, an RIE process. The fin201 material is removed down to the level of about the substrate 202.With an ideal mask overlay as shown in FIG. 3B, two shorter fins 201would be formed in the cross-sectional view through the Y-axis (FIG.4C). However, the poor mask overlay (FIG. 3C) results imperfect fincutting, as shown in FIG. 4C, where the fin 201 is only partiallysevered. The partial fin cut is also shown in FIG. 4A beneath the fincut opening 312 where only a portion of the hard mask 222 and fin 201material is removed in the region 413. In the region 414, the fins 201are completely cut into two shorter fins.

FIG. 5A is a top view after oxidizing the end portions of the fins 201to form an oxide layer 501. FIGS. 5B and 5C are cross-sectional sideviews through the X-axis and Y-axis, respectively, of FIG. 5A. An oxidelayer 501 is formed along a sidewall (endwall) of the first ends 514 andsecond ends 515 of the cut fins 201. The surface of the material formingthe fins 201 and substrate 202 oxidize after being cut and exposed toair. In one embodiment, the fins 201 and substrate 202 are formed fromsilicon and the oxide layer 501 includes silicon dioxide. The oxidelayer 501 forms beneath the hard mask 222 and along sidewalls (endwalls)between the fins 201, as shown in FIG. 5C.

The oxide layer 501 forms by employing a thermal oxidation process.Thermal oxidation is performed at a temperature in a range from about300 to about 1100° C., which provides a High Temperature Oxide layer(HTO). Water vapor (e.g., steam) or molecular oxygen may be used as theoxidant. The oxidizing ambient also may include hydrochloric acid (HCl).

The thickness of the oxide layer 501 along any sidewall (or endwall)(first send 514 or second end 515) may generally vary and is notintended to be limited. In one embodiment, the thickness of the oxidelayer 501 is in a range from about 3 to about 10 nanometers (nm). Inanother embodiment, the thickness of the oxide layer 501 is in a rangefrom about 4 to about 6 nm. In other embodiments, the fin 201 materialis oxidized to form an oxide layer 501 that is at least half the finwidth 530, or critical dimension (CD).

In some embodiments, the thickness of the oxide layer 501 in the region502 between the fins 201 (along one sidewall/endwall of the fins 201) isthicker than the oxide layer 501 along another sidewall of the fins 201.In other embodiments, the thickness of the oxide layer 501 along asidewall of the first end 514 is different than the thickness of theoxide layer 501 along a sidewall of the second end 515. The thickness ofthe oxide layer 514 along a sidewall of the first end 514 may be thickeror thinner than the thickness of the oxide layer 501 along a sidewall ofthe second end 515. In one embodiment, the oxide layer 501 forms anasymmetric liner with varying thicknesses of the oxide layer alongdifferent sidewalls (first end 514 and second end 515) of the fins 201.

FIG. 6A is a top view after disposing a liner 620 and a planarizationlayer 610 over the fins 201. FIGS. 6B, 6C, and 6D are cross-sectionalside views through the X-axis, Y-axis, and Z-axis, respectively, of FIG.6A. The Y-axis view in FIG. 6C shows the partially cut fins 201 inregion 413 (see FIG. 4A). The Z-axis view in FIG. 6D shows thecompletely cut fins 201 in region 414 (see FIG. 4A).

The liner 620 is deposited as a blanket layer over the exposed fin hardmasks 222 and over the oxide layer 501. As shown in FIG. 6C, the liner620 is only deposited along a single sidewall of the partially cut fins(first end 514 and second end 515) (see region 413 in FIG. 4A). Theoxide layer 501 and the liner 620 form a bilayer liner along a sidewallof the first end 514. The oxide layer 501 forms a monolayer liner alonga sidewall of the second end 515.

In FIG. 6D, when the fins 201 are completely cut through fin cut opening312 (see FIG. 4A), a bilayer liner including the oxide layer 501 and theliner 620 are formed along sidewalls of the first and second ends 514,515.

The liner 620 includes an insulating hard mask material. Non-limitingexamples of suitable materials for the liner 620 include siliconnitride, SiOCN, SiBCN, or any combination thereof. The thickness of theliner 620 may generally vary and is not intended to be limited. In oneembodiment, the thickness of the liner 620 is in a range from about 1 toabout 10 nm. In another embodiment, the thickness of the liner 620 is ina range from about 2 to about 5 nm. The liner 620 material is formedusing a suitable deposition process, for example, chemical vapordeposition (CVD) or physical vapor deposition (PVD).

The planarization layer 610 may be, for example, an OPL coating or othersuitable spin-on coating. The planarization layer 610 may include anorganic material, for example, a polymeric material.

FIG. 7A is a top view after patterning the planarization layer 610 toform a fin cut pattern 710 (second fin cut pattern). FIGS. 7B, 7C, and7D are cross-sectional side views through the X-axis, Y-axis, andZ-axis, respectively, of FIG. 7A. The fin cut pattern 710 exposes theliner 620. The fin cut pattern 710 exposes the liner 620 over the fins711 to be removed.

The planarization layer 610 is patterned by disposing an etch mask (notshown) over the planarization layer 610. The etch mask (not shown) maybe a resist material, for example, a photoresist material. Theplanarization layer 610 is patterned by removing the planarization layer610 material by, for example, a dry etching process (e.g., an RIEprocess or a plasma ashing process). The liner 620 over the fins 201 isexposed.

FIGS. 8A, 8B, and 8C are cross-sectional side views through the X-axis,Y-axis, and Z-axis, respectively, after removing the liner 620 and hardmask 622 over the fins 201. The liner 620 and hard mask 622 are removingby employing an etching process. The etching process may be, forexample, a dry etching process (plasma etching or reactive ion etching(RIE).

FIGS. 9A, 9B, and 9C are cross-sectional side views through the X-axis,Y-axis, and Z-axis, respectively, after removing the planarization layer610. The planarization layer 610 is removed. The planarization layer 610is removed, by, for example, a plasma ashing process.

FIGS. 10A, 10B, and 10C are cross-sectional side views through theX-axis, Y-axis, and Z-axis, respectively, after removing the fin 201material from the exposed fins 201 (fins 711). The fins 711 (unwantedfins) are removed by employing an isotropic etching process (a secondetching process). Isotropic etching removes the fin 201 material via achemical process using an etchant substance. Non-limiting examples ofisotropic etchants include hydrofluoric acid, hydrofluoric nitric acid,phosphoric acid, or any combination thereof. Other non-limiting examplesof suitable isotropic dry etching processes include FRONTIER siliconetching isotropic processes (Applied Materials, Santa Clara, Calif.).The fin 201 material is selectively removed. The oxide layer 510 aroundthe fins 1001 (desired fin material not to be removed) acts as an etchstop to protect the fins 1001.

FIGS. 11A, 11B, and 11C are cross-sectional side views through theX-axis, Y-axis, and Z-axis, respectively, after removing filling theremoved fin regions with oxide 1101 to form STI regions. The oxide 1101may be the same or different than the material forming the STI regions230. Non-limiting examples of oxides include silicon dioxide,tetraethylorthosilicate (TEOS) oxide, high aspect ratio plasma (HARP)oxide, silicon oxide, high temperature oxide (HTO), high density plasma(HDP) oxide, oxides (e.g., silicon oxides) formed by an atomic layerdeposition (ALD) process, or any combination thereof. A planarizationprocess, for example, chemical mechanical planarization (CMP), isperformed to polish the surface of the oxide 1101.

FIG. 12A is a top view after etching the oxide 1101 to reveal the uncutfins 201. FIGS. 12B, 12C, and 12D are cross-sectional side views throughthe X-axis, Y-axis, and Z-axis, respectively, of FIG. 12A. The liner 620and hard mask 222 over the fins 1001 are removed. The oxide 1101 and STIregions 230 are recessed to reveal the uncut fin tips 1201. The oxide1101 and STI regions 230 are etched (recessed) by an amount in a rangefrom about 20 to about 50 nm. The oxide 1101 and STI regions 230 may beetched by a process using dilute hydrofluoric acid (DHF) or by anetching process employing simultaneous exposure H₂, NF₃, and NH₃ plasmaby-products (SiCoNi etching).

The oxide layer 501 is recessed by performing an etching process. Theoxide layer 501 may be recessed, by, for example, a process usingbuffered hydrofluoric acid (BHF) or DHF. The liner 620 may be recessedby performing an etching process, for example, a process including hotphosphoric acid. The oxide layer 501 and the liner 620 are recessed toabout the level of the recessed oxide 1101.

As shown in FIG. 12C, some fins 201 include an asymmetric liner (seealso, FIG. 6C). The fin 201 includes a bilayer liner along one sidewallof the first end 514 and a monolayer liner along a sidewall of thesecond end 515.

As shown in FIG. 12D, other fins 201 include a symmetric liner (seealso, FIG. 6D). The fin 201 includes a bilayer liner along sidewalls ofthe first end 514 and the second end 515.

As described above, various embodiments provide methods of cutting fins(or removing undesired fin portions) without jeopardizing the desiredfin portions in devices with closely spaced fins. Thermal oxidation isused to seal fin ends in a two-step fin cutting method includinganisotropic and isotropic etching processes. Thermal oxidation protectsthe fins to ensure substantially complete removal of undesired finportions.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, element components,and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

The flow diagrams depicted herein are just one example. There may bemany variations to this diagram or the steps (or operations) describedtherein without departing from the spirit of the invention. Forinstance, the steps may be performed in a differing order or steps maybe added, deleted or modified. All of these variations are considered apart of the claimed invention.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A method of making a semiconductor device, the method comprising: patterning a fin in a substrate; performing a reactive ion etch process to remove a portion of the fin and to cut the fin into a first cut fin and a second cut fin, the first cut fin having a first fin end and a second fin end, and the second cut fin having a first fin end and a second fin end; performing a thermal a thermal oxidation process to form an oxide layer on an endwall of the first fin end and an endwall of the second fin end of the first cut fin, and an endwall of the first fin end and an endwall of the second fin end of the second cut fin, a thickness of the oxide layer on the endwall of the first fin end of the first cut fin being different than a thickness of the oxide layer on the endwall of the first fin end of the second cut fin; disposing a liner comprising an insulating material onto the oxide layer disposed on the endwall of the first fin end of the first cut fin to form a bilayer liner comprising the liner and the oxide layer, the liner not being disposed on the second fin end of the first cut fin; and performing an isotropic etch process comprising a chemical etchant to remove a portion of the second cut fin, the oxide layer protecting the first cut fin from being etched during the isotropic etch process. 